1. Field of the Invention
The present invention relates to a method of manufacturing a multilayer ceramic electronic component, and more particularly, it relates to an improvement of a pressing step which is applied to an unfired laminate formed by stacking a plurality of ceramic green sheets with each other.
2. Description of the Background Art
Among multilayer ceramic electronic components, a multilayer ceramic capacitor, for example, is typically manufactured through the following steps:
First, a plurality of ceramic green sheets are prepared. Then, conductor films for serving as internal electrodes are formed on specific ones of the ceramic green sheets. These conductor films are formed by applying metal paste onto the ceramic green sheets by printing. Then, the metal paste is dried and the plurality of ceramic green sheets are stacked with each other, so that the laminate as obtained is pressed in the direction of stacking.
The aforementioned laminate is generally planned to be cut in advance of firing, so that a plurality of chips for forming multilayer ceramic capacitors are taken out. In the aforementioned step of forming the conductor films for serving as internal electrodes, therefore, the conductor films are distributed in a plurality of portions of each ceramic green sheet.
The laminate as pressed is then cut as described above to obtain a plurality of chips, which in turn are fired. External electrodes are applied to each of the chips as fired, thereby providing a desired multilayer ceramic capacitor.
However, the pressing step included in the aforementioned method of manufacturing a multilayer ceramic capacitor may often result in a laminate 1 which is in a situation shown in FIG. 2. While conductor films 2 for serving as internal electrodes must be aligned with each other in the laminate 1 along the direction of stacking, the same tend to deviate along the outer peripheral direction of the laminate 1 in a central portion of the laminate 1 along its thickness upon pressing. Such deviation of the conductor films 2 is accumulated toward outer peripheries of the laminate 1, leading to relatively large deviation in those of the conductor films 2 which are in proximity to the outer peripheries of the laminate 1.
The aforementioned deviation of the conductor films 2 leads to such inconvenience that the multilayer ceramic capacitor as obtained is dispersed in capacitance and no desired capacitance can be obtained. Further, a gap 3 between adjacent sets of the conductor films 2 shown in FIG. 2 is so reduced that a cutting line may undesirably pass through the conductor films 2 in the cutting step following the pressing step, to cause inconvenience of defective cutting.
In addition, it may be difficult to apply a press action on regions around the conductor films provided in the laminate due to presence of the conductor films, and hence the ceramic sheets may be insufficient in adhesive strength in these regions. This may result in a problem of delamination in the subsequent steps or the products as obtained. This problem of delamination is particularly remarkable in a laminate formed by a large number of conductor films which are stacked with each other.
When the plurality of ceramic green sheets are stacked with each other, further, air may be entrained between these green sheets, to result in voids. While such voids must be removed through the pressing step, some may occasionally remain after the pressing step. Such voids particularly remarkably remain when the number of the stacked conductor films exceeds 30, for example. The voids remaining through the pressing step are brought into the finally obtained multilayer ceramic electronic component as such, since the voids are not removed in the subsequent steps. As the result, the multilayer ceramic electronic component encounters problems of delamination, reduction in moisture resistance, deterioration of electric characteristics and the like.